The invention relates to welding. More particularly, the invention relates to beam welding of a first item to a second item at hidden discrete contact locations.
The difficulty of blind welding has plagued the field of milled channel heat exchangers. One example of a milled channel heat exchanger is the wall of a rocket nozzle as shown in Damgaard et al. “Laser Welded Sandwich Nozzle Extension for the RL60 Engine” (AIAA-2003-4478), AIAA, Reston, Va., 2003, the disclosure of which is incorporated by reference herein as if set forth at length. In an exemplary milled channel heat exchanger, an array of channels are milled in a base material leaving ribs between the channels. A cover sheet or panel is placed atop the ribs and welded thereto (e.g., via laser or e-beam from the side of the sheet facing away from the base layer). Registering the welding beam with the ribs has proven difficult. X-ray apparatus have been proposed. X-ray devices, however, may be expensive and difficult to use.